1. Field of the Invention
The present invention relates to press controls generally and, more specifically, to a novel press control activation system for hand fed power presses and like machines that is self-contained, includes an anti-tie-down feature that cannot be defeated, and eliminates the possibility of an operator developing carpel tunnel syndrome from repeatedly pressing buttons.
2. Background Art
Hand fed power presses and like machines are widely used in the manufacturing industries in a variety of punching, stamping, shearing, and similar operations. Typically in such an operation, the operator places a piece of sheet metal or similar piece of stock to be punched, stamped, sheared, or the like in position in the machinery. Since the operation is extremely hazardous, it is necessary to ensure that the both of the operator's hands are clear of the operating area before the machinery is operated, or "tripped," to initiate the operating cycle. Conventionally, such has been ensured by requiring the operator to simultaneously or nearly simultaneously depress two spaced apart switches, one with each hand, in order to trip the machinery. After the sheet metal or stock is operated on, the machinery returns to its non-operating position and the operator is free to use his hands to remove the part.
A disadvantage of some conventional tripping systems is that one switch could be "tied-down" by placing an object against it, for example, and thus the operator would have one hand free to perhaps increase the overall speed of the operation and, therefore, his productivity. To combat this procedure, anti-tie-down controls have been incorporated into the machinery controls so that the switches have to be depressed simultaneously or nearly simultaneously and that depression of the switches has to be maintained throughout the operation. A disadvantage of this type of system, however, is that, since the timed and anti-tie-down circuitry is separate from the switches and is readily accessible, the circuitry can be defeated easily by the operator or other persons - or simply omitted from the installation. Likewise, since the heavy duty relays that provide power to the machinery are also provided as separate components, further opportunity to defeat safety features is available.
A further disadvantage of some conventional tripping systems is that, although the force required to operate a spring-loaded switch is perhaps only a few ounces, the repetition of the pressing motion by the operator over a period of time tends to lead to the development of painful tunnel carpel syndrome in the hands of the user. Besides being painful to the operator, such job-related illnesses are costly to the manufacturers and to the insurance carriers. This problem has been overcome in some tripping systems through the use of capacitive proximity switches which do not require exerting pressure to activate them. Unfortunately, such capacitive proximity switches heretofore employed have been extremely sensitive, being activatable by liquids such as by merely spraying glass cleaner on them. Obviously, such sensitivity presents a serious safety hazard.
Accordingly, it is a principal object of the present invention to provide a press control system in which power relays and anti-tie-down circuitry are an integral part thereof and cannot be defeated.
It is a further object of the invention to provide such a press control system which does not require the pressing of buttons to operate, yet cannot be operated by the presence of oil, water, or other liquids that may be present in the manufacturing area.
It is another object of the invention to provide such a press control system which can be easily retrofitted to existing machinery.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.